What are the initial lab tests and treatment for a patient suspected of having Immune Thrombocytopenic Purpura (ITP)?

Initial Laboratory Workup for Suspected ITP

The diagnosis of ITP requires a complete blood count (CBC) with peripheral blood smear examination, with additional testing primarily focused on excluding other causes of thrombocytopenia rather than confirming ITP itself. 1

Essential Initial Laboratory Tests

Mandatory First-Line Tests

• CBC with differential and peripheral blood smear review by a qualified hematologist or pathologist is paramount—this demonstrates isolated thrombocytopenia (platelet count <100 × 10⁹/L) without anemia or leukopenia, and shows normal or large platelets without schistocytes, leukocyte inclusion bodies, or other abnormalities inconsistent with ITP 1, 2

• Reticulocyte count helps distinguish whether any anemia present results from bleeding (iron deficiency with elevated reticulocytes) versus bone marrow failure 1

• HIV and HCV testing is recommended for all adult patients regardless of risk factors, as thrombocytopenia from these infections is clinically indistinguishable from primary ITP and can occur years before other symptoms develop 1

Important Exclusionary Tests

• Peripheral smear must exclude pseudo-thrombocytopenia from EDTA-dependent platelet agglutination, which can falsely suggest thrombocytopenia 1

• Coagulation studies (PT, aPTT, fibrinogen) should be obtained to exclude disseminated intravascular coagulation (DIC), which typically shows abnormal coagulation parameters unlike ITP where these remain normal 3

Tests NOT Routinely Required

• Bone marrow examination is NOT necessary for typical ITP presentation at any age, and should only be performed if there are abnormalities beyond isolated thrombocytopenia (such as anemia, leukopenia, or abnormal peripheral smear findings) 1

• Antiplatelet antibody testing is not routinely recommended as platelet-associated IgG is elevated in both immune and non-immune thrombocytopenia, lacking diagnostic specificity 1

Additional Testing to Consider

Infectious Screening

• Helicobacter pylori testing (preferably urea breath test or stool antigen test) should be considered in adults where it may have clinical impact, though routine testing in children is not supported except in high-prevalence areas 1

• HBV testing should be included alongside HIV and HCV screening 1

Pregnancy-Specific Testing

• Blood pressure measurement and liver function tests are appropriate to rule out preeclampsia as an alternative diagnosis in pregnant women 1

• Blood group Rh(D) typing is important if anti-D immunoglobulin treatment is being considered 1

Tests of Potential Utility (Not Routine)

• Antinuclear antibodies (ANA) may predict chronicity in childhood ITP but are not routinely required 1

• Thyroid function testing and antithyroid antibodies may identify patients at risk for clinical thyroid disease, as 8-14% of ITP patients develop hyperthyroidism longitudinally 1

• Direct antiglobulin test (DAT) should be checked to rule out concurrent Evans' syndrome (combined ITP and autoimmune hemolytic anemia) 1

Critical Diagnostic Pitfalls

Splenomegaly is NOT consistent with typical ITP—the spleen should be normal size in adults and palpable in only ~12% of pediatric cases (particularly infants); a palpable spleen suggests alternative diagnoses such as myelodysplasia, thalassemia, or lymphoproliferative disorders 4

Schistocytes on peripheral smear exclude ITP and suggest thrombotic thrombocytopenic purpura (TTP) or other thrombotic microangiopathies, requiring immediate ADAMTS13 testing 3, 5

Refractory thrombocytopenia should prompt reconsideration of the diagnosis—particularly myelodysplastic syndrome with isolated thrombocytopenia (MDS-IT), which can present with multilineage dysplasia, normal karyotype, and low-risk prognostic scores, requiring bone marrow examination with cytogenetic testing 6

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Initial Treatment for ITP

Treatment should be administered for newly diagnosed adult patients with platelet counts <30 × 10⁹/L, or at any platelet count with active bleeding. 1

First-Line Treatment Options

Corticosteroids (Preferred Initial Therapy)

• Longer courses of corticosteroids are preferred over shorter courses or IVIg as first-line treatment for adults 1

• Prednisone 1 mg/kg/day orally (dosage range 0.5-2 mg/kg/day) for 4 weeks followed by taper over 4-6 weeks to the lowest effective dose 1

• High-dose dexamethasone 40 mg daily for 4 days may be considered as an alternative to prednisone 1

Intravenous Immunoglobulin (IVIg)

• IVIg should be used with corticosteroids when a more rapid increase in platelet count is required (such as active bleeding or need for urgent procedures) 1

• Initial dose: 1 g/kg as a one-time dose, which may be repeated if necessary 1

• IVIg or anti-D (in appropriate Rh-positive patients) should be used as first-line treatment if corticosteroids are contraindicated 1

Anti-D Immunoglobulin

• May be used in Rh-positive, non-splenectomized patients as an alternative to IVIg when corticosteroids are contraindicated 1

Treatment Based on Severity

Severe Life-Threatening Bleeding

• Immediate hospitalization with high-dose parenteral corticosteroids, IVIg, AND platelet transfusions for patients with severe, life-threatening hemorrhage 1, 2

• Platelet transfusions are NOT recommended for less severe bleeding and should be reserved for critical hemorrhage 2

Platelet Count-Based Treatment Thresholds

• Platelet count >50 × 10⁹/L: No routine treatment required unless active bleeding 1

• Platelet count 30-50 × 10⁹/L: Treatment generally not required unless bleeding or high bleeding risk 1

• Platelet count <30 × 10⁹/L: Treatment recommended 1

• Platelet count <10 × 10⁹/L: Treatment required regardless of bleeding symptoms 1

Pregnancy-Specific Treatment

• Pregnant women with platelet counts >50 × 10⁹/L do not routinely require treatment and should not receive glucocorticoids or IVIg as routine initial therapy 1

• Treatment is required for pregnant women with platelet counts <10 × 10⁹/L, or those with counts 10-30 × 10⁹/L in second or third trimester who are bleeding 1

• IVIg is appropriate initial treatment for women with platelet counts <10 × 10⁹/L in the third trimester 1

• Maternal platelet count >50 × 10⁹/L is considered sufficient to prevent excessive bleeding at vaginal delivery or cesarean section 1

Second-Line Treatment (After Corticosteroid Failure)

Splenectomy

• Splenectomy is recommended for patients who have failed corticosteroid therapy and remains a definitive treatment option 1

• Both laparoscopic and open splenectomy offer similar efficacy for medically suitable patients 1

Thrombopoietin Receptor Agonists

• Recommended for patients at risk of bleeding who relapse after splenectomy or have contraindications to splenectomy and have failed at least one other therapy 1

• May be considered for patients at risk of bleeding who have failed one line of therapy (such as corticosteroids or IVIg) and have not had splenectomy 1

Rituximab

• May be considered for patients at risk of bleeding who have failed one line of therapy such as corticosteroids, IVIg, or splenectomy 1

Pediatric Treatment Considerations

• High-dose dexamethasone may be considered for children or adolescents with significant ongoing bleeding despite treatment with IVIg, anti-D, or conventional corticosteroid doses 1

• Splenectomy should be delayed for at least 12 months unless accompanied by severe disease unresponsive to other measures or significant quality of life considerations 1